1. Field of the Invention
The present invention relates to a fuel hose for supplying fuel drawn up from an automobile fuel tank to the fuel injection valves of the engine, and to a method for manufacturing this fuel hose.
2. Description of the Related Art
A fuel hose has conventionally been provided to the fuel supply system connecting an automobile fuel tank to the engine. FIG. 11 is a simplified structural diagram of a fuel supply system. In FIG. 11, an end of a metal fuel pipe 106 is connected to an automobile fuel tank 102 via a fuel pump 104. Other end of the fuel pipe 106 is connected to and supported by a filter 110 fixed to a dash panel 108. A fuel hose 112 is connected to the outlet of the filter 110, and supplies fuel to the fuel injection valves 116 of the engine. The fuel hose 112 is usually formed from a rubber material, but there has been a changeover to resin materials in recent years in an effort to reduce weight and cost.
However, resinous fuel hoses have caused problems. When fuel is injected from the fuel injection valves 116, there is a sudden drop in the fuel supply pressure within the fuel hose 112. The sudden drop in fuel supply pressure becomes a pulse that propagates from the fuel hose 112 to the fuel pipe 106 and vibrates the dash panel 108 through the filter 110. This causes noise.
At the least, the above-mentioned noise grates on the ear and is unpleasant to hear when operating an automobile. Accordingly, use of pulsation dampers has been required to reduce noise. Use of pulsation dampers, however, increases the number of parts, defeats the attempt to lower weight and adds to the cost of the system.
Another problem was that the fuel hose 112 was disposed in the cramped space of the engine compartment, with vibrations that occurred as the fuel supply pressure rose and fell interfered with other items in the engine compartment.
It is an object of the present invention to provide a fuel hose made of resin, which reduces noise during fuel injection into an engine and does not interfere with other engine components.
The first embodiment of the present invention, conceived in order to solve the above problems, is a fuel hose configured to supply fuel drawn up from a fuel tank to fuel injection valves of an engine.
The hose includes a main body with a fuel passage, in which the main body is made of.
The hose includes a non-circular component formed integrally with the hose main body, with the non-circular component having a plurality of ribs each extending in an axial direction along the hose main body. The ribs are constructed and arranged to vary the cross section of the non-circular component when a fuel pressure is applied to the fuel hose, thereby absorbing pulsating pressure occurring within the fuel hose.
The fuel hose pertaining to the first embodiment of the present invention supplies fuel drawn up from a fuel tank to the fuel injection valves of an engine. This fuel hose has a non-circular component with a plurality of ribs running in an axial direction along the hose main body. This non-circular component expands and contracts radially in response to pressure fluctuations that accompany fuel injection by the fuel injection valves. As a result, the non-circular component varies its volume capacity greatly during fuel injection in response to fluctuations in the fuel pressure inside the fuel hose, which attenuates the vibrations and suppresses the generation of noise. Thus, even if a resin material, that is lower in cost than rubber material, is used for the fuel hose, the effects of pulsation accompanying fuel injection can be reduced and noise suppressed to the same or greater extent than with a rubber hose.
Since a considerable pulse absorbing effect is thus provided by the non-circular component with this fuel hose, there is no need to use pulsation dampers as was described for the prior art, which affords a reduction in the number of parts.
Also, the changes in the shape of the non-circular component that accompany pressure fluctuations are primarily just in the radial direction, and there is no expansion and contraction in the axial direction, that is, along the axial direction of the fuel hose. Accordingly, expansion or contraction of the fuel hose causes no change in the path of the fuel hose, there is no interference with other nearby members, and there is no noise generated or any reduction in durability.
An example of a favorable shape for the non-circular component is for a plurality of ribs to be equidistantly disposed in ridges running in the axial direction of the fuel hose.
In a preferred embodiment of the first embodiment of the present invention, a bellows component is formed adjacent to the non-circular component in the axial direction of the hose. With this structure, if the fuel hose winds around a curved path, it can be easily bent in bellows area, and any movement of the non-circular component in the axial direction brought about by expansion and contraction can be restricted by the bellows component. Thus, the fuel hose can be easily routed through a cramped installation space in the engine compartment.
In another embodiment of the present invention, there are further provided a circular component that has a circular cross section that is connected to one end of the bellows component, and a tapered component that connects the circular component and the noncircular component whose cross sectional shape gradually varies from the cross sectional shape of the circular component to that of the non-circular component shape.
In addition to connecting to an ordinary pipe with a circular cross section, the non-circular component may be connected to a bellows component and/or an ordinary pipe. For example, a structure in which an ordinary pipe connects the non-circular component to the bellows component can be adopted by taking into account various parameters such as the pulse absorption action, mechanical strength, and routing of the hose. In this case, in order to facilitate routing, instead of employing a structure which bends at a bellows area, the fuel hose may be bent by pre-bending an ordinary pipe.
The material from which the fuel hose is formed can be a polyamide-, fluorine-, polyester-, polyketone-, or polysulfide-based resin, a thermoplastic elastomer, or an ethylene/vinyl alcohol copolymer. A plasticizer may also be added to the fuel hose to increase the flexibility of the fuel hose.
It is preferable for the fuel hose to be formed such that it will absorb pressure fluctuations of approximately 0.02 MPa on either side of a 0.3 MPa internal hose pressure of the liquid flowing through the fuel hose.
It is also preferable for the fuel hose to be formed such that the proportional volumetric change is at least 7 mmxe2x80x2/(MPaxe2x88x92mm). The term proportional volumetric change as used here refers to the amount of volumetric change when the pressure changes by 1 MPa per millimeter of fuel hose.
The present invention also includes a method for manufacturing a fuel hose.
The method includes a first step of forming a hose main body with a circular cross section by first extruding a resin material, and then in a second step forming a non-circular componentin the circular cross-sectional area. The non-circular section includes a plurality of ribs that extend in the axial direction along the hose main body. The cross sectional shape of the ribs can vary with the pressure on the fuel flowing through the fuel hose.
This manufacturing method allows non-circular components of different cross sectional shapes to be manufactured continuously and easily.
The second step preferably includes a step in which the non-circular component is formed with the ribs equidistantly disposed in ridges running in the axial direction along the fuel hose.
The second step may also include a step in which a bellows component is provided adjacent to the non-circular component in the axial direction.
In addition, the second step may also include a step of forming a circular component that has a circular cross section and is connected to one end of the bellows component, and a tapered component that inter-connects the circular component with the non-circular component, with cross sectional shape of the tapered component gradually varying from the cross sectional shape of the circular component to that of the non-circular component.
The second step may further include a step in which molds having molding surfaces for forming the circular component, the non-circular component, and the bellows component. Such molds may be disposed in a loop and move through a molding area. The circular component, the non-circular component, and the bellows component are formed in a desired sequence on the molding surfaces in the desired molds. The molding surfaces are connected to passages to which suction is applied by a suction pump so that the material will conform to the desired cross-sectional shape of the circular component, the non-circular component, and the bellows component.